1. Field of the Invention
This invention relates to a photo-electric converting device used in a distance measuring device for measuring the distance to an object to be photographed or an object located at a specific spot.
2. Description of the Prior Art
There have been known distance measuring devices which to compute the distance to an object and the extent to which a photo-taking lens should be shifted for focusing it on the object to be photographed and to shift the photo taking lens to an in-focus position and stop it in that position.
Such a device includes therein a photo-electric converting device which receives the reflected light from the object to produce an electric charge quantity signal through a photo-electric conversion process and gives a distance measuring signal based on the electric charge quantity signal.
Heretofore, a highly sensitive and highly responsive photo-electric converting element has been employed as the above photo-electric converting element. Some of such devices discriminate a projected light from an external light through a synchronized integrating operation to statistically eliminate the influence of the external light and thus to take out only the reflected light component resulting from a light projecting operation. However, because of the scale of the synchronized integrating operation, the integrating arrangement cannot be made using the same IC as that of a photo-electric converting arrangement. As a result, such photo-electric converting elements have increased probability of noise generation due to the use of amplifiers, etc.
Furthermore, in storage type photo-electric converting elements using a CCD or the like in general, external light information other than effective information is also stored. Therefore, due to the limited dynamic range of the CCD employed, it has been impossible to obtain an adequate S/N ratio.
It is a first object of the present invention to provide a photo-electric converting device wherein light emitting means which emits and projects distance measuring light on a distance measuring or photography object which performs the light emitting action alternately with no light emitting action.
It is a second object of the invention to provide a photo-electric converting device which is of a simple structure and which facilitates use of an integrated circuit.
It is a third object of the invention to provide a photo-electric converting device which comprises photo-electric converting means which receives from an object reflected light resulting from a light projected by light emitting means continuously performing light emitting and another reflected light from the object resulting from sunlight or indoor illuminated light (or an external light).
It is a fourth object of the invention to provide a photo-electric converting device wherein there are provided a photo-electric converting part, a first storing part which stores an electrical signal representing a reflected light quantity received from the above object when light emitting is performed by the above light emitting means, a second storing part which stores an electrical signal representing a reflected light quantity received from the object when no light is emitted from the light emitting means, a computing part which computes storage signals produced from the first and second storing parts and produces a distance measurement signal therefrom, transfer gates which permit transfer of the storage signals from the storing parts to the computing part for the above computation and a gate control part which controls these gates; and wherein with the alternately repeating cycle of light emitting and no light emitting of the light emitting means utilized, reflected light at the time of light emission and another reflected light at the time of no light emission are received by the single photo-electric converting part; the photo-electric conversion signals obtained at these times are stored respectively at the first and second storing parts; and a reflection light component resulting solely from light emitting is obtained through computation.
The general and common objective of the first through fourth objects of the invention is to provide a device wherein there is provided one photo-electric converting part.
A fifth object of the invention is to provide a photo-electric converting device wherein a photo-electric converting part receiving an incident light is divided into first and second parts.
These and further objects and features of the invention will become apparent from the detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.